Blood meal digestion by female mosquitoes is a complex physiological process. Proteins are the predominant components of blood and 24 hours after feeding 80 percent of the ingested protein has been digested. This is possible because the blood meal induces a large increase in midgut proteolytic activity, with trypsin representing the main endoproteolytic enzyme. In fact, two different trypsin forms (early and late) are expressed during blood meal digestion and the regulation of trypsin synthesis involves control at both the translational and transcriptional level. The relationship between the activity of early trypsin and the transcription of the late trypsin gene represents a unique regulatory system that is control by blood feeding. In this proposal we seek funds to continue work on the mechanism of regulation of early and late trypsin synthesis in the midgut of female Aedes aegypti following a blood meal and to begin exploring other midgut specific genes whose regulation is affected by blood feeding. Specifically, we proposed to 1) Investigate the mechanism of activation of translation of the early trypsin mRNA following a blood meal. 2) Investigate the mechanism of transcriptional regulation of the late trypsin gene. 3) Characterize cis-regulatory elements in the early and late trypsin genes. 4) Identify additional midgut proteins involved in the maturation of the midgut following eclosion and/or in processing the blood meal. The results of these studies will be important in furthering our understanding of the regulation of blood meal digestion in mosquitoes - a key event in the life cycle of this medically important insect. Beyond that, these experiments will identify key DNA sequence elements involved in the regulation of midgut-specific and blood-feeding regulated genes. Such promoter sequences may prove valuable in ongoing experiments to develop mosquito transformation systems as a strategy for mosquito control.